Matric Part 1/9th Class Physics Chapter 6 Long Question With Answer for Unit 6 Work and Energy

Question # 1

Define work. when a force do work? explain

Ans 1: Work: work is said to be done when a force acts on a body and moves it in the direction of the force.
Recognition of work: the question raised how much work is done? naturally, greater is the force acting on a body longer is the distance moved by it, larger would be work done
" work is done when a force acting on a body displaces it in the direction of force".
Ans 2: Quantity: work is scaler quantity
Ans 3: Dependence; it depends on the force acting on the body, displacement of the body and angle between them.
Ans 4: unit: its unit is joule(J)
Ans 5: Definition: if one newton force act on the body it covers one meter distance in the direction of force, then its work will be one joule
1J= 1N*1m

Question # 2

How is energy converted from one form to another? Give some examples

Ans 1: Interconversion of energy: the conversion of one form of energy into another form is called interconversion of energy.
Explanation: energy cannot be destroyed however it can be converted into some other forms . For example, rub your hands together quickly. You will feel them warm. You have used your muscular energy in rubbing hands as a result heat is produced. In the process of rubbing mechanical energy is converted into heat energy. Processes in nature are the results of energy changes. For examples, some of the heat from the sun is taken up by water in the oceans. This increases thermal energy. Thermal energy causes water to evaporate from the surface to form water vapors. These vapors rise up and form clouds. As they cool down, they form water drops and fall down as rain. Potential energy changes to kinetic energy as the rain falls . This rain water may reach a lake or a dam. As the rain water flows down, its kinetic energy changes into thermal energy while parts of kinetic energy of flowing water is used to wash away soil particles of rocks known as soil erosion. During the interconversion of energy from one form to other forms, the total energy at any time remains constant .

Question # 3

What is meant by renewable sources of energy?

Ans 1: Renewable source of energy: the source of energy which wil not run out and can be used again and again are called renewable sources of energy
Example:
- Energy from water
- solar energy
- wind energy
- geothermal energy
- energy from biomass
Ans 2: Energy from water: water is a big source of production of energy in the form of electricity.
Energy from water power is very cheap. Dams are being constructed at suitable locations in different parts of the world. In dams, such stored water possesses potential energy due to its height. When this water stored at a height is allowed to fall down it is used to run power plants. These power plants convert the P.E of stored water into electricity. This electricity is then supplied thorough electric wires in the country.
Ans 3: Solar energy: solar energy is the energy coming from the sun.
Importance of solar energy:
- Solar energy can be used directly and indirectly
- Sunlight does not pollute the environment
- The sunrays are the ultimate source of life on the earth
- We are dependent on the sun for all our food and fuels
Ans 4: Wind energy: moving air is called a wind and energy possessed by the wind is called wind energy
Uses of wind energy: wind has been used as a source of energy for centuries
- It has powered sailing ships across the oceans
- It has been used by windmills to grind grain and pump water
- More recently, wind power is used to turn wind turbines
Ans 5: Geothermal energy: in some parts of the world, the earth provides us hot water rom geysers and hot springs. There is hot molten part, deep in the earth , called magma. Water reaching close to the magma changes to steam due to the high temperature of magma. This energy is called geothermal energy.
Conversion of geothermal energy into useful fuels: geothermal well can be built by drilling deep near hot rocks places, where magma is not very deep. Water is then pushed down into the well. The rocks quickly heat the water and change it into steam. This steam expands and moves up to the surfaces of earth. The steam can be pipe directly into house and offices for heating purposes or it can be used to generate electricity.
Biomass: biomass is plant or animal wastes that can be burnt as fuel. Other forms of biomass are garbage, farm wastes , sugarcane and other plants.
Energy from biomass: there are different ways tot get energy from biomass. Some of these are as follow
- Different forms of biomass are used to run power plants
- Many industries that use forest products get half of their electricity by burning bark and other wood wastes.

Question # 4

What are nuclear fuels? explain it

Ans 1: nuclear fuels: the materials through which we can obtain nuclear energy are called nuclear fuels e.eg uranium element. In nuclear power plants wee get energy as a result of fission reactions.
Ans 2: Nuclear fission reaction: the process in which heavy nucleus breaks into two smaller nuclei releasing a loti of energy is called nuclear fission reaction. During fission reaction, heavy atoms splits into two smaller parts releasing large amount of energy.
Ans 3: Example: fission reaction of uranium element
Ans 4: Uses: nuclear power plants give out a lot of nuclear radiations and a vast amount of heat. A part of this heat is used to run power plants while a lot of heat goes waste into environment

Question # 5

Explain the mass-energy equation

Ans 1: Einstein predicted the interconversion of matter and energy. According to him, a loss in the mass of a body provides a lot of energy. This happen in the nuclear reaction. The relation between mass m and energy E is given by Einstein's mas-energy equation
E=mc²
Where c is the speed of light( 3*10⁸ ms^-1)
Ans 2: Significance; the above equation shows that tremendous amount of energy can be obtained from sample quaintly of matter. It happens that matter is highly concentrated form of energy
Ans 3: Uses: the process of getting the energy from our nuclear power plants is based on the above equation. The process is taking place on the sun and stars for the last millions of yeas. Only a very small fraction of the suns energy reaches the earth. This very small fraction of the suns energy is responsible for life on the earth.

Question # 6

Q no:6 (B) A 50 kg man moved 25 steps up in 20 seconds. Find his power , if each step is 16 cm high.

Ans 1: m= 50 kg
Height of h= 16 cm
each step = 0.16m
n= 25
t = 20s
p= ?
Since
F = w
= mg
= 50 x 10
= 500N
Height = h= 0.16 x 25 = 4m
reached by man
As we know that
P =w/t = F x s/t
By putting the values
P= 500 x y/20
= 2000/20
= 100w Ans

Question # 7

Q no:(B) Calculate the power of a pump which can lift 200 kg of water through a height of 6 meters in 10 seconds.

Ans 1: M= 200kg
h= 6 m
t= 10s
power of the pump = p=?
Since
F= w
= mg
200 x 10
=2000n
As we know that
p=w/t =F x s/t
But putting the values , we have
p= 2000 x6/10
p=m12000/10
P = 1200 W Ans

Question # 8

Define power and explain its units

Ans 1: Power is defined as the rate of doing work.
Mathematically:
Power=P= work done / time taken
P=W/t
Ans 2: Quantity: work is a scaler quantity. Therefore , power is also a scaler quantity.
Ans 3: Unit: SI unit of power is watt(W)
Ans 4: Watt: the power of a body is one watt if it does work at the rate of 1 joule per second ( 1 Js^-1)
Formula:
1W = 1j / 1s
Ans 5: Bigger units : bigger units of power are kilowatt , megawatt etc
1KW=1000W=10³W
!MW=1000000W=10⁶W
1hp=746W

Question # 9

Q no: 7(A) Write is the uses of Wind Energy.?

Ans 1: Wind Energy:
Wind energy has used as a source of energy for centuries. It has powered sailing ships across the oceans . It has been used by windmills to grind grain and pump water. More recently , wind power is used to turn wind turbines. When many wind machines are grouped together on wind farms , they can generate enough power to operate a power plant. In the United stated , some wind farms generate more than 1300 MW of electricity a day. In Europe, many wind farms routinely generate hundred megawatts or more electricitya day

Question # 10

Define potential energy, explain its types

Ans 1: potential energy: the energy possessed by a body due to its position is called potential energy.
Examples:
- Stored water possesses the potential energy due to its height
- A hammer raised up to some height has the ability to do work because it possesses potential energy
Ans 2: Types:
- Elastic potential
- gravitational potential energy
Ans 3: Elastic potential energy; the energy present in a body due to the starched position is called elastic potential energy.
Example: a stretched bow has potential energy due to its stretched position
Ans 4: Gravitational potential energy: the energy present in a body due to its highest position is called gravitational potential energy.
Example: the energy possessed by a hammer due to its height
Ans 5: Explanation; let a body of mass m be raised up thorough height h from the ground. The body will acquire potential energy equal to the work done in lifting it to the height h.
Thus;
potential energy=P.E=F*h=w*h
P.E= mgh (here weight of body = w=mg)
Thus, the potential energy possessed by the body with respect to the ground is mgh and is equal to the work done in lifting it to height h.

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Matric Part 1/9th Class Physics Chapter 6 Long Question With Answer for Unit 6 Work and Energy

9th Class English Medium Subjects

9th Class Urdu Medium Subjects

Online Long Questions For Chapter 6 "9th Class Physics Chapter 6 Long Question Preparation "

Physics (New Book) - 9th Class Physics Chapter 6 Long Question Preparation

Define work. when a force do work? explain

How is energy converted from one form to another? Give some examples

What is meant by renewable sources of energy?

What are nuclear fuels? explain it

Explain the mass-energy equation

Q no:6 (B) A 50 kg man moved 25 steps up in 20 seconds. Find his power , if each step is 16 cm high.

Q no:(B) Calculate the power of a pump which can lift 200 kg of water through a height of 6 meters in 10 seconds.

Define power and explain its units

Q no: 7(A) Write is the uses of Wind Energy.?

Define potential energy, explain its types

Prepare Complete Set Wise Questions For Chapter 6 "9th Class Physics Chapter 6 Long Question Preparation "

Set 1

Set 2

9th Class Physics Chapter 6 Long Question Preparation - Set 1

Define work. when a force do work? explain

How is energy converted from one form to another? Give some examples

What is meant by renewable sources of energy?

What are nuclear fuels? explain it

Explain the mass-energy equation

Q no:6 (B) A 50 kg man moved 25 steps up in 20 seconds. Find his power , if each step is 16 cm high.

Q no:(B) Calculate the power of a pump which can lift 200 kg of water through a height of 6 meters in 10 seconds.

Define power and explain its units

Q no: 7(A) Write is the uses of Wind Energy.?

Define potential energy, explain its types

9th Class Physics Chapter 6 Long Question Preparation - Set 2

Q no: 7(A) Write is the uses of Wind Energy.?

What is energy converter ?

Q no:5(A) Define potential energy. Give its examples and derive its equation P.E = mgh.

What is efficiency? explain working of an ideal system.

Define energy and explain kinetic energy

Write and explain energy conversion processes involved in producing of electricity

Define work. when a force do work? explain

Q no:(B) Calculate the power of a pump which can lift 200 kg of water through a height of 6 meters in 10 seconds.

Define power and explain its units

How is energy converted from one form to another? Give some examples

9th class Physics Chapter 6 Long Q's (English Medium)